VoIP for Dummies 2005
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238 Part V: Appendixes
Appendix B
Glossary
Numbers
911: The standard number for emergency telephone calls made over the public switched telephone network (PSTN) in North America. See also E911.
A
access: A generalized term referring to the physical means (such as POTS line or T1 line) through which a carrier company provides telecommunications services to a customer.
access cost: The one-time installation charges plus the recurring costs for access to one or more network services, such as Internet access.
add-on charges: Monthly charges beyond access costs. Add-on charges are mandated by the government and administered by the carrier. These types of add-on charges are also referred to as regulatory fees.
analog: A method of representing voice signals through a variation in the amplitude, frequency, or phase of an electrical signal. POTS telephone lines originally used (and in many areas continue to use) analog transmission to gain access to the public telephone network.
application layer: The top layer of the TCP/IP model. The application layer is where a packet is first encoded or last decoded. For the sender, it is the layer at which an application first presents information to the protocols to be packetized. For the receiver, it is the layer at which information is finally depacketized and ready for use by the application.
area code: A three-digit code that represents a specific geographic calling area in North America. The area code is dialed first in the sequence of calling any telephone number. Some areas, depending on population size, do not require an area code for calls made within the local regional calling area.
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asymmetric transmission: When the upstream and downstream transmission rates are different; for example, the upload rate may be 256 Kbps and the download rate 1.536 Mbps. Most consumer broadband networks use asymmetric transmission.
B
B channel: A bandwidth unit employed by the integrated services digital network (ISDN). An ISDN B channel delivers 64 Kbps of digital bandwidth over the public switched telephone network (PSTN).
bandwidth: A measure of the amount of data that can be transmitted during a set period of time. In most cases, the terms bandwidth and speed are used synonymously. The bandwidth of a communications channel is often expressed in Kbps (kilobits per second) or Mbps (megabits per second).
bandwidth allocation: Digital bandwidth can be subdivided and allocated based on channels. For example, a T1 line with an aggregate bandwidth of 1.536 Mbps can allocate eight 64 Kbps channels to the telephone system, eight channels to the computer data network, and eight channels to a videoconferencing system. All 24 channels can be used in a dynamic allocation pool. A pool assigns channels as needed for the life of the telephone or videoconference call and returns the channels to the pool when the call or session is over.
basic rate interface: BRI. The consumer-grade level of ISDN service. A BRI consists of two B channels of 64 Kbps per channel. The two channels can be used in aggregate, or each channel can be dedicated to a specific application. A BRI also includes a D channel, which is a 16 Kbps channel used strictly by the carrier to manage services over the BRI line.
BRI: Basic rate interface. The consumer-grade level of ISDN service. A BRI consists of two B channels of 64 Kbps per channel. The two channels can be used in aggregate, or each channel can be dedicated to a specific application. A BRI also includes a D channel, which is a 16 Kbps channel used strictly by the carrier to manage services over the BRI line.
broadband: In general usage, a communications channel capable of transmission speeds equal to or greater than 256 Kbps. There is not currently a clear definition on the maximum speed for broadband. It also describes two popular services (DSL and cable modem) that connect consumers and small businesses to the Internet.
Appendix B: Glossary 241
C
cable modem: A popular form of broadband service that runs over the consumer’s cable television network transport line to offer access to the Internet.
call control: A PSTN management technology that establishes a connection, keeps the call up, and tears the call down when the parties hang up. Call control provides an automated means to track and manage call-related information for billing and maintenance.
call forwarding: A calling feature that enables the telephone customer to forward inbound telephone calls to another telephone number before ringing at the original destination number.
call transfer: A calling feature that enables the telephone customer to transfer an in-process telephone call to another telephone number.
calling feature: Additional uses or applications of the telephone, the telephone line, or the network that carries the telephone call. Voice mail, call forwarding, and call transfer are examples of traditional calling features. VoIP telephony has all the traditional calling features plus a new generation of features that use the telephone and the network, such as presence, vemail, and displaying a Web page on your telephone screen.
carrier: The company responsible for the transport lines used to provide communications services. Carriers lease transport lines to customers and often provide the services that operate over those lines, such as voice, data, and video transmission.
carrier services company: See carrier.
carrier services provider: See carrier.
carrier services infrastructure: CSI. Refers to a subset of five network types available in the telecommunications domain. Network transport lines for a particular CSI are available by leasing through carriers.
Centrex: Central Office Exchange. Centrex uses POTS lines to provide PBXlike services and features to customers.
channelization: The capacity for subdividing and allocating bandwidth channels in a dedicated transport line. For example, a DS3 transport line provides 672 channels of 64 Kbps each. Channelization allows those channels to be independently utilized for different communication purposes.
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circuit-switched: The traditional method of transporting a telephone call over the PSTN. Multiple devices known as switches are employed by the carriers to form paths, or circuits, over which telephone calls may be carried between a caller and a receiver.
CLEC: Competitive local exchange carrier. Before the Telecommunications Act of 1996, the term interexchange carrier (IXC) was more commonly used. CLECs are the carriers that sought to lease transport lines and services to customers within an area where the Local Exchange Carriers (LECs) owned all the lines. The 1996 law mandated that the LECs (now ILECs) must lease their local lines at wholesale prices to CLECs. In return, the regulation promised to open the long-distance markets to ILECs. See also ILEC.
competitive local exchange carrier: CLEC. Before the Telecommunications Act of 1996, the term interexchange carrier (IXC) was more commonly used. CLECs are the carriers that sought to lease transport lines and services to customers within an area where the Local Exchange Carriers (LECs) owned all the lines. The 1996 law mandated that the LECs (now ILECs) must lease their local lines at wholesale prices to CLECs. In return, the regulation promised to open the long-distance markets to ILECs. See also ILEC.
compression: In digital networking, a method of reducing the bit length of network traffic (that is, packets) to enable more efficient data transmission.
convergence: The integration of switched and dedicated networks to support similar applications. For example, using VoIP on the corporate computer network to place a call on the traditional public telephone network.
CSI: Carrier service infrastructure. CSI refers to a subset of five network types available in the telecommunications domain. Network transport lines for a particular CSI are available by leasing through carriers.
D
D channel: A channel used by ISDN transport services. A BRI includes a 16Kbps D channel, and a PRI includes a 64-Kbps D channel. These channels are used strictly by the carriers to manage services over the customer’s ISDN line.
dedicated access: A classification of access using a private network transport (T1, T3, or OC3 line) through which a carrier provides ultra-high bandwidth telecommunications services to an individual customer.
Appendix B: Glossary 243
dedicated network: A network dedicated to a single customer and implemented through the use of dedicated access lines.
delay: The total time it takes for a signal to travel from the source to the destination.
digital: A fast, efficient method of representing voice signals through high and low pulses. Since the inception of digital networking techniques, many newer, faster, and more precise methods of networking have become available.
digital service: DS. The initial form of the digital service CSI through which the first digital, private, dedicated transport lines (such as DS1 and DS3 lines) were installed beginning in 1964.
digital subscriber line: DSL. A popular form of broadband service which runs over a POTS line to provide Internet access. In most cases, DSL service requires the consumer to have an existing POTS line service.
digital telephony: Started first as a method for carriers to aggregate and transport POTS telephone calls on the carrier’s network using DS-type transport lines. This same technology would later be redeveloped into privately owned telephone systems (PBX) that would be owned and operated by customers.
DS: See digital service.
DS0: One 64-Kbps channel of digital bandwidth on the DS network.
DS1: The standard for 24 DS0 channels having an aggregate bandwidth of 1.536 Mbps. A DS1 line is also known as a T1 line.
DS3: The standard for 672 DS0 channels having an aggregate bandwidth of 45 Mbps. A DS3 line is also known as a T3 line.
DSL: Digital subscriber line. A popular form of broadband service which runs over a POTS line to provide Internet access. In most cases, DSL service requires the consumer to have an existing POTS line service.
DWDM: Dense wave division multiplexing. A newer network transport service that aggregates network traffic for transmission in the terabit bandwidth ranges.
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E
E911: An enhanced form of the standard number for emergency telephone calls made over the traditional PSTN in North America. E911 automatically provides, to the 911 call center agent, the caller’s contact information, including name, address, and telephone number. The E911 system also has the capability to provide contact information to first responders, including police, fire, and paramedic personnel within the caller’s local calling area.
encapsulation: A process whereby network traffic (data, voice, or video) is formatted according to the requirements of the network protocol (Ethernet or TCP/IP) being used to transport the traffic. The LAN encapsulates traffic into MAC frames. The WAN encapsulates traffic into packets.
encryption: A process that secures network traffic from unauthorized access. By using secure procedures or secure software keys known only to authorized users, the encrypted network traffic can be accessed.
Ethernet: The oldest and most popular protocol used for establishing data networks. Ethernet is used in more than 98 percent of corporate America for LAN networking. Ethernet is increasingly being used as a MAN backbone standard. The fundamentals of Ethernet are modified slightly to support WiFi and WiMax, popular forms of wireless Ethernet. See also IEEE 802.3, IEEE 802.11, and IEEE 802.16.
extensibility: An attribute of networks that allows them to be enlarged or enhanced without the need to change basic network characteristics.
F
feature: Additional uses or applications of the telephone, the telephone line, or the network that carries the telephone call. Voice mail, call forwarding, and call transfer are examples of traditional calling features. VoIP telephony has all the traditional calling features plus a new generation of features that use the telephone and the network, such as presence, vemail, and displaying a Web page on your telephone screen.
feature cost: Charges associated with the implementation of calling features. In traditional POTS telephony, calling features have a cost associated with them, typically in the form of additional monthly charges.
Appendix B: Glossary 245
fiber optic: A physical cable medium used in most networks for all outside segments of the network’s physical layer.
firewall: Software or hardware that limits access to a data network. Some firewall systems also provide network management functions.
frame: On the LAN side of the network, bit signal traffic is encapsulated and transported inside MAC frames. See also MAC.
G
gateway: A network device used to provide access between different types of networks. For instance, a gateway may provide access into an external network such as the PSTN, the Internet, or a private WAN. A PSTN gateway has a LAN interface on the inside and a PRI access transport line on the outside. It translates IP telephony frames from the LAN into circuit-switched POTS traffic for the PSTN and vice versa.
H
hard phone: A VoIP-enabled telephone that has an RJ-45 LAN interface port to connect it to the Ethernet LAN. VoIP telephones today come in all shapes and sizes.
HFC: Hybrid fiber-coaxial. The CSI that supports cable television, broadband services, and VoIP telephony through cable modem and POTS telephony through a POTS telephone and adapter.
hop: On the Internet, a hop represents a single, intermediary step in the path of a network transmission from the source to the destination.
hosted VoIP: A managed VoIP telephony service similar in concept to the traditional Centrex model. Synonymous with IP Centrex, VoIP Centrex, hosted telephony, and hosted VoIP telephony.
hybrid fiber-coaxial: HFC. The CSI that supports cable television, broadband services, and VoIP telephony through cable modem and POTS telephony through a POTS telephone and adapter.
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I
IEEE: Institute for Electrical and Electronic Engineers. The main standardscertifying body for protocols such as Ethernet (IEEE 802.3), WiFi (IEEE 802.11), and WiMax (IEEE 802.16).
IEEE 802.3: The standard defining early forms of the Ethernet networking protocol.
IEEE 802.11: The standard defining early forms of wireless Ethernet (WiFi).
IEEE 802.16: The standard defining a form of WiFi known as WiMax designed to handle higher bandwidths over greater distances.
ILEC: Incumbent local exchange carrier. Introduced with the Telecommunications Act of 1996. ILEC is intended to identify the carrier who owns the traditional, regulated cabling infrastructure in any given LATA. See also CLEC.
in-state toll: One of four traditional regulated toll carrier service categories, also known as intrastate.
integrated services digital network: ISDN. A group of digital transport services that use the circuit-switched PSTN. ISDN transports are capable of integrating data, voice, and video applications, but run slower than other transports available today.
interexchange carrier: IXC. Dominated the long-distance carrier services marketplace before the implementation of the Telecommunications Act of 1996.
international: One of four traditional regulated toll carrier service categories. Considered to be the most highly regulated of all toll services.
Internet: A global, publicly accessible, nonregulated, nonsecure network accessible from all five CSIs.
Internet service provider: ISP. A company that provides Internet access to consumers and companies. Larger and more versatile ISPs offer Internet access using a variety of network transport options.
interstate toll: One of four traditional regulated toll carrier service categories, also known as long distance.
Appendix B: Glossary 247
intralata toll: One of four traditional regulated toll carrier service categories, also known as local toll or regional toll. Refers to calls in which the caller and receiver are in the same local access and transport area (LATA).
intranet: A private network based on the same protocols used on the larger public Internet. Those outside the network can gain access to a corporate intranet through a firewall or gateway, if the network is configured to allow such access.
intrastate toll: One of four traditional regulated toll carrier service categories, also known as in-state toll.
IP: Internet Protocol. One of two major protocols used in the TCP/IP family of protocols. The IP protocol is one of the protocols used to implement the Internet.
IP address: An address comprised of four numbers, each ranging from 0 to 255, and normally expressed with each number separated by a period (such as 192.168.2.100). IP addresses are used to route network traffic from sender to receiver. The IP address is a major component field of a VoIP packet and is used to map the VoIP telephone call to a specific telephone number. In a VoIP telephony call, both source and destination (caller and receiver) addresses are used to establish and maintain the VoIP call.
IP Centrex: A managed VoIP telephony service similar in concept to the traditional Centrex model. Synonymous with VoIP Centrex, hosted VoIP, hosted telephony, and hosted VoIP telephony.
IP soft phone: Software that enables a computer to function as a VoIP telephone, including an on-screen dialing pad for point-and-click dialing.
IP telephony: IPT. A technology that allows traditional voice calls to be carried as data over a local area network. IPT is technically VoIP on a LAN (and VoIP is IPT outside the LAN).
IPT: IP telephony. A technology that allows traditional voice calls to be carried as data over a local area network. IPT is technically VoIP on a LAN (and VoIP is IPT outside the LAN).
ISDN: Integrated services digital network. A group of digital transport services that use the circuit-switched PSTN. ISDN transports are capable of integrating data, voice, and video applications, but run slower than other transports available today.